Induction of micronuclei and sister chromatid exchange in bone-marrow cells and abnormalities in sperm of Algerian mice (Mus spretus) exposed to cadmium, lead and zinc

As a consequence of human activities, large amounts of cadmium, lead and zinc are released in the environment, often simultaneously. The aim of this study was to investigate under experimental conditions the DNA damage induced in Algerian mice (Mus spretus) exposed to cadmium (Cd), lead (Pb) and zinc (Zn) separately, or in selected combinations. Three cytogenetic end points were considered: the frequencies of micronucleated cells (MN) and sister chromatid exchange (SCE) in the bone marrow and the frequency of sperm abnormalities. Mice were treated by intraperitoneal (i.p.) injections with 5 or 10 doses of aqueous solutions of cadmium acetate, lead acetate and zinc acetate in concentrations corresponding to 1/10 of the LD50, respectively, 21.5, 0.46 and 1.5 mg/kg bw. The control groups were injected in the same way with distilled water.With only one exception (Cd + Zn group treated with 5 doses), the results show a significant increase of MN in all groups for both treatments (5 and 10 doses). Similarly, the results concerning the SCE revealed a statistically significant increase in all treated animals, with the exception of the Zn group treated with 5 doses. The number of sperm abnormalities was significantly higher in animals treated with 5 doses, except in the group Pb + Zn. In animals treated with 10 doses the number of sperm abnormalities was always statistically higher compared with controls.This study indicates that cadmium, lead and zinc can induce MN, SCEs and sperm abnormalities in Algerian mice and that the clastogenic potential is dependent on the time of exposure and the interaction between the three elements, confirming the environmental damage that may result from the simultaneous action of several metals. Most relevant is the toxic potential for Zn, related with the dose, which may compromise its protective effect against other metal contaminations, such as cadmium.     

Laboratory evaluation of avermectin as a selective acaricide for use withMetaseiulus occidentalis (Nesbitt) (acarina: Phytoseiidae)

The suggestion that adding a light oil to avermectin B₁ would increase the toxicity of avermectin to spider mites and reduce its effect on predaceous mites was tested in laboratory trials withTetranychus urticae Koch andMetaseiulus occidentalis (Nesbitt) on almond and bean foliage. No differences were found in the toxicity of avermectin + oil vs. avermectin alone at the doses tested forT. urticae; all (0.025, 0.5, 1, and 5 ppm) were highly toxic. Mortality ofM. occidentalis females and larvae was not different on avermectin + oil vs. avermectin alone, but females produced more progeny on the avermectin + oil-treated foliage. At doses of 0.5 to 5 ppm, avermectin was sufficiently toxic to deplete predator populations in the field. Development of predator larvae on avermectin + oil and on avermectin alone was not different. Avermectin + oil on almond foliage aged outdoors was highly toxic after 96 h toT. urticae adults butM. occidentalis larvae survived well on residues by 96 h.M. occidentalis female survival and productivity were not different from the controls by 48 h. Hence a predator mite population might recover through larvae hatching onto residues. Avermectin + oil (3 ppm) residue on bean foliage held outdoors was still highly toxic toT. urticae after 33 days. In contrast,M. occidentalis females and larvae survived well on 48-to 96-hour-old residues. Neither predators nor spider mites placed on treated foliage (3 ppm) were able to reach untreated foliage in tests using bean plant seedlings with one leaf sprayed and one left unsprayed. Furthermore, whenM. occidentalis females were exposed to 3 ppm avermectin for 300 s or longer, mortality was significant and the fecundity of females that had been exposed for as few as 30 s was reduced significantly. Thus, while avermectin is significantly more toxic toT. urticae than toM. occidentalis, its value as a selective acaricide will depend upon learning to use it at rates that will allow the retention of sufficient prey so that surviving predators can persist. Based on these laboratory tests, such selective doses are likely to lie below 1 ppm and can best be determined in field trials.     

Effects of ozone on some biological activities of cellsin vitro

The aim of this work was to study thein vitro effect of ozone on the 70 kDa family of inducible heat shock proteins (HSPs 70). We also performed tests to investigate possible toxic effects of ozone at the different doses employed. In human haematic mononucleated cells ozone at doses up to 20 g/ml had no toxic effects and induced biosynthesis of the HSPs70. Biosynthesis of these proteins was greater at 40 g/ml. In murine macrophages testing with tetrazolium salt (MTT), neutral red, and 2-deoxy-d-[1-³H]glucose uptake and study of the cell morphology showed a remarkable resistance or no toxic effects at a dose of 100 g/ml also. Melanoma B16 murine cells assayed with the MTT test demonstrated less resistance to the toxic effects of ozone than normal cells. These results provide indications relevant to the problems of ozone therapy.Abbreviations ConA concanavalin A - HHMC human haematic mononucleated cells - HSPs70 70 kDa family heat shock proteins - LPS lipopolysaccharide - MTT (3-(4,5-dimethylthiazol-2-yl)-diphenyltetrazolium bromide) - NR neutral red - PHA phytohaemagglutinin - TPA 1,2-O-tetradecanoylphorbol 1,3-acetate     

The study of the Ca2+ role in cytotoxic response of human cells in culture to the action of xenobiotics

The role of Ca2+ in mechanisms of cell death, necrosis and apoptosis is diverse and generally recognized. The purpose of this work was to study Ca2+ participation in a cytotoxic response of human cultured cells in the presence of toxic concentrations of cationic antiseptic substance poly(hexamethylene guanidine), anionic surfactant SDS and monomeric methyl methacrylate (a component of bone cement applied in surgery). Human cell line U-937 grown in suspension was used for this study. A fluorescent probe chlortetracycline was used, as an indicator of Ca2+ transport through biologic membranes. Our results show that weakly toxic concentrations of xenobiotics under study, close to the minimum toxic doses, nearly always provoke a fair but statistically significant drop in Ca2+ binding by cells. At the same time, higher toxic doses lead to significant increase in Ca2+ influx. The latter event well compares with the majority of literary data, while the mentioned decrease in Ca2+ influx at low toxic concentrations of xenobiotics presumably correlates with the initial stage of acute cytotoxic response, accompanied by a metabolic activation and enhanced resistance of cells to injuring stimuli, demonstrated by the authors elsewhere. In parallel, a possible effect of Ca(2+)-channel antagonist nifedipine was explored under conditions of cytotoxic response of cell lines U-937, A-549 and human embryonic lung fibroblasts to poly(hexamethylene guanidine). Nifedipine (10 microM) was introduced in the incubation medium simultaneously with the toxic agent, and the cells were further maintained for 5 or 24 h in culture; their viability was monitored with the microtetrasolium test or by assessment of LDH leakage into the incubation medium. The effect of nifedipine proved to be dual, depending on the applied concentration of toxic agent: at low toxic concentrations the improvement of viability could be noticed, while at more pronounced toxic doses aggravation of viability was evident. From our point of view the explanation of this result could be the following. In weakly toxic conditions, as in intact cells, Ca2+ influx is brought about by specific mechanisms, mainly through Ca(2+)-channels, that is why nifedipine partly abolishes Ca(2+)-dependent cytotoxic response. At high concentrations, cell plasma membrane is directly damaged by toxic agent, Ca2+ enters cells mainly non-specifically, so that Ca2+ antagonist cannot protect cell injury. The reason of toxic effect aggravation by nifedipine in these conditions is still waiting for its explanation.     

Selective effects of two systemic fungicides on soil fungi

BAS 317 00F was not toxic to the total count of fungi after 2 days but was regularly significantly toxic at the three doses after 5, 20 and 40 days and toxic at the low and the high doses after 80 days. In the agar medium, it was toxic to the counts of total fungi, Aspergillus, A. terreus, Rhizopus oryzae and Mucor racemosus at the high dose. Only the mycelial growth of Trichoderma viride which was significantly inhibited by the three doses when this fungicide was added to the liquid medium.Polyram-Combi induced two effects on the total population of soil fungi. One inhibitory and this was demonstrated almost regularly after 2, 10 and 40 days and the other stimulatory after 80 days of treatment with the low and the high doses. In the agar medium, this fungicide was very toxic to total fungi and to almost all fungal genera and species at the three doses. Several fungi could survive the high dose. In liquid medium, the test fungi showed variable degree of sensitivity and the most sensitive was Gliocladium roseum which was completely eradicated by the three doses.     

Toxic effects caused by heavy metals in the yeast Saccharomyces cerevisiae: a comparative study

The decreasing order of toxicity of select heavy metals on the yeast Saccharomyces cerevisiae, in 10 mM MES (2-(N-morpholino)ethanesulfonic acid) pH buffer at pH 6.0, was found to be copper, lead, and nickel. Heavy metal (200 microM) induced a decrease in the number of viable cells by about 50% in the first 5 min for copper and in 4 h for lead, while nickel was not toxic up to a 200 microM concentration over a period of 48 h. Glucose (25 mM) strongly enhanced the toxic effect of 50 microM copper but had little or no effect on the toxicity of 200 microM lead or nickel. Copper, lead, and nickel induced the leakage of UV260-absorbing compounds from cells with different kinetics. The addition of 0.5 mM calcium, before addition of 200 microM copper, showed a protective action against cell death and decreased the release of UV-absorbing compounds, while no effect was observed against lead or nickel toxic effects. Copper complexation capacities of the filtrates of cells exposed for 2 h in 200 microM copper and 24 h in 200 microM lead were 51 and 14 microM, respectively. The implication of the complexation shown by these soluble compounds in the bioavailability of heavy metals is discussed.     

Synthetic human monoclonal antibodies toward staphylococcal enterotoxin B (SEB) protective against toxic shock syndrome

Staphylococcal enterotoxin B (SEB) is a potent toxin that can cause toxic shock syndrome and act as a lethal and incapacitating agent when used as a bioweapon. There are currently no vaccines or immunotherapeutics available against this toxin. Using phage display technology, human antigen-binding fragments (Fabs) were selected against SEB, and proteins were produced in Escherichia coli cells and characterized for their binding affinity and their toxin neutralizing activity in vitro and in vivo. Highly protective Fabs were converted into full-length IgGs and produced in mammalian cells. Additionally, the production of anti-SEB antibodies was explored in the Nicotiana benthamiana plant expression system. Affinity maturation was performed to produce optimized lead anti-SEB antibody candidates with subnanomolar affinities. IgGs produced in N. benthamiana showed characteristics comparable with those of counterparts produced in mammalian cells. IgGs were tested for their therapeutic efficacy in the mouse toxic shock model using different challenge doses of SEB and a treatment with 200 μg of IgGs 1 h after SEB challenge. The lead candidates displayed full protection from lethal challenge over a wide range of SEB challenge doses. Furthermore, mice that were treated with anti-SEB IgG had significantly lower IFNγ and IL-2 levels in serum compared with mock-treated mice. In summary, these anti-SEB monoclonal antibodies represent excellent therapeutic candidates for further preclinical and clinical development.     

Motor behavior and brain enzymatic changes after acute lead intoxication on different strains of mice

Lead is a nonphysiological metal that has been implicated in toxic processes that affect several organ systems in humans and other animals. Although the brain generally has stronger protective mechanisms against toxic substances than other organs have, exposure to lead results in several neurophysiological and behavioral symptoms. The administration of a single injection (i.p.) of lead acetate in mice is a model of acute Pb2 + toxicity. In the present study, this model was used to explore the magnitude of the effect of different doses, time intervals and mice strains on several biobehavioral parameters. We investigated the effects of acute lead acetate administration on body and brain weight, brain lead acetate accumulation and specially, spontaneous locomotion and brain catalase activity. Lead acetate was injected i.p. in outbred (Swiss or CD1) and inbred (BALB/c, C57BL/J6 or DBA/2) mice at doses of 0, 50, 100, 150 or 200 mg/kg. At different time intervals following this acute treatment, several biochemical, physiological and behavioral responses were recorded. Results indicated that acute lead acetate has deleterious dose-dependent effects on brain and body weight. The effect on body weight in the present study was transient, although lead acetate was detected in neural tissues for several days after administration. Spontaneous locomotor activity only was reduced up until 24 hours. The effect of lead on body weight was strain-dependent, with Swiss mice showing greater resistance compared to the other strains. Total brain catalase activity in lead-pretreated Swiss mice showed a significant induction. This enzymatic upregulation could provide a protective mechanism for oxidative stress in these mice.     

Asymmetric effects of litter removal and litter addition on the structure and function of soil microbial communities in a managed pine forest

Aims

The effect of different MeJA doses applied prior to or simultaneously with toxic Al on biochemical and physiological properties of Vaccinium corymbosum cultivars with contrasting Al resistance was studied.

Methods

Legacy (Al-resistant) and Bluegold (Al-sensitive) plants were treated with and without toxic Al under controlled conditions: a) without Al and MeJA, b) 100 μM Al, c) 100 μM Al + 5 μM MeJA, d) 100 μM Al + 10 μM MeJA and e) 100 μM Al + 50 μM MeJA. MeJA was applied to leaves 24 h prior to or simultaneously with Al in nutrient solution. After 48 h, Al-concentration, lipid peroxidation (LP), H₂O₂, antioxidant activity, total phenols, total flavonoids, phenolic compounds and superoxide dismutase activity (SOD) of plant organs were analyzed.

Results

Al-concentrations increased with Al-treatment in both cultivars, being Al, LP and H₂O₂ concentrations reduced with low simultaneous MeJA application. Higher MeJA doses induced more oxidative damage than the lowest. Legacy increased mainly non-enzymatic compounds, whereas Bluegold increased SOD activity to counteract Al³⁺.

Conclusions

Low MeJA doses applied simultaneously with Al³⁺ increased Al-resistance in Legacy by increasing phenolic compounds, while Bluegold reduced oxidative damage through increment of SOD activity, suggesting a diminution of its Al-sensitivity. Higher MeJA doses could be potentially toxic. Studies are needed to determine the molecular mechanisms involved in the protective MeJA effect against Al-toxicity.

     

Comparison of tin and lead toxic action on erythropoietic system in blood and bone marrow of rabbits

The aim of this work was to assess and compare morphological changes in blood and bone marrow of rabbits afterper os (po) or intraperitoneal (ip) administration of equimolar doses of tin or lead. The experiment was performed on female rabbits that were divided into four groups of six animals each, and received stannous chloride SnCl₂×2 H₂O (Merck) or lead acetate Pb(CH₃COO)₂ (POCh Gliwice) in equimolar doses (ip—17/uM/kg) orper os (po—85/uM/kg). Group I was administered SnCl₂ ip at the dose of 2 mg Sn/kg every day for 3 mo, group II Pb(CH₃COO)₂ ip at a dose of 3.5 mg Pb/kg every day for 3 wk, group III po SnCl₂ (10 mg Sn/kg), and group IV po Pb(CH₃COO)₂ (17.5 mg Pb/kg), both for 4 mo. The morphological factors hemoglobin (Hb), hematocrit (Ht), erythrocyte (Ercs), and reticulocyte counts, MCV, MCH, MCHC, and erythropoietic system in bone marrow aspirates with sideroblast count, iron concentration, TIBC, and SI were estimated. Tin caused hemolytic anemia depending on abnormal iron utilization. After ip administration of tin, anemia was observed during the whole time of the study, whereas after po exposure, transient anemia was noticed. It has been proven that the mechanism of toxic action of tin on hematopoietic system is similar to the toxic effect of lead.     

Comparative toxicity of Pfiesteria spp., prolonging toxicity of P. piscicida in culture and evaluation of toxin(s) stability

Toxicity of Pfiesteria piscicida (strain CAAE #2200) in the presence of fish (juvenile hybrid tilapia, Oreochromis sp., total length 3–6 cm) has been maintained in the laboratory for 19 months by serial transfer of toxic cells using a modified maintenance protocol. Toxicity was re-induced when toxin-producing P. piscicida cells were separated from fish and cultured on algal prey for 50 days and then re-introduced to new tanks containing fish. We confirmed toxicity in a strain of P. shumwayae (strain CAAE #101272). Toxicity to fish was demonstrated in culture filtrates (0.2 μm) derived from cultures of both Pfiesteria spp., however, it was markedly reduced in comparison to unfiltered water. Filtrates retained toxic activity when stored at −20 °C for up to 6 months. Toxicity to fish was retained when filtrates were held at room temperature for 48 h, at 70 °C for 30 min or at 88–92 °C for 2 h. P. piscicida killed all finfish species tested. Grass shrimp (Paleomonetes pugio; adult 2–3 cm), blue crab (Callinectes sapidus; juvenile 4–7 cm) and brine shrimp (Artemia sp.; 18–24 h post-hatch) were unaffected by concentrations of toxin(s) that killed juvenile tilapia in 4–24 h. Ichthyotoxic activity of filtrates from fish-killing cultures and stability of the toxic activity were similar among P. piscicida and P. shumwayae. These results confirm previously reported observations on toxicity of P. piscicidaand P. shumwayae to finfish. We have maintained toxicity in the laboratory for longer periods than have previously been routinely achieved, and we have demonstrated that the toxic activity is heat stable. In contrast to previous studies with other toxic P. piscicida strains, we did not observe toxic activity to blue crabs or other crustaceans.     

Chronotherapeutic Dose Schedule of Phenytoin and Carbamazepine in Epileptic Patients

The objective of this study was to compare the efficacy and safety of a chronotherapeutic dosing schedule of phenytoin and carbamazepine versus a conventional dosing schedule for the treatment of tonic‐clonic epileptic patients. Of 148 epileptic subjects found to have subtherapeutic trough drug levels (subtherapeutic group, STG), 103 subjects who completed the study were randomized to either STG I (n=51) for treatment by the conventional dosing schedule (tablet phenytoin 100–400 mg/day OD or BD, tablet carbamazepine 200–800 mg BD, or both, equally divided doses with no fixed time of drug intake), with a dose increment but no change in usual time of drug administration allowed; or to STG II (n=52), with no dose increment permitted but a shift in all or most (two‐thirds or three‐fourths) of the daily dose of one or both medications to 20:00 h. The 62 patients who experienced drug toxicity reactions (toxicity group, TG) and who had serum drug levels in the toxic range were assigned to TG I for dose reduction or TG II for dose reduction and drug administration at 20:00 h. Those 16 subjects in STG I and 47 subjects in STG II who initially evidenced subtherapeutic trough drug concentrations exhibited therapeutic drug levels by the end of four weeks of treatment (p<0.01). A significantly greater number of TG II, as compared to TG I, subjects who experienced toxic reactions showed improved drug tolerance. There were no poor responders and more good responders (control of epilepsy for one year) in STG II compared to STG I subjects. The findings of this study indicate that a chronotherapeutic dosing schedule of phenytoin and carbamazepine involving the administration of most or all the daily dose of medication(s) at 20:00 h can improve the response of diurnally active epileptic patients not responding to standard doses, achieve therapeutic drug levels, and reduce toxic manifestations in subjects having drug concentrations beyond the therapeutic range.     

Kinetic study of the toxicity of zinc and lead ions to the heavy metals accumulating fungus Paecilomyces marquandii

Studies have been carried out to determine the toxicity of zinc and lead ions to germinating spores and hyphal growth of heavy metal accumulating fungus Paecilomyces marquandii (former Verticillium marquandii). Inhibitive concentration (IC₅₀) of zinc and lead ions was assayed by three different methods: image analysis, nephelometric on-line measurement and microcalorimetry. A kinetic model of spore germination and germ tube elongation was formulated and used as an auxiliary tool to determine IC₅₀ values upon image analysis data. The inhibitive effect of Zn²⁺ and Pb²⁺ to P. marquandii spores was mathematically described by the Edwards equation. Comparing the obtained IC₅₀ values, lead ions occurred to be more toxic to the germinating spores of P. marquandii than zinc ions (2.80 and 5.20 mM, respectively), although zinc ions induced a more significant delay in the development of the hyphae (13.84 h for 5 mM of Zn²⁺ and 9.30 h for 5 mM of Pb²⁺), which was demonstrated by the lengthened lag-phase (spore-swelling phase).     

Alterations in calcium homeostasis on lead exposure in rat synaptosomes

The effects of lead on Ca²⁺ homeostasis in nerve terminals was studied. Incubation with leadin vitro stimulated the activity of calmodulin and the maximum effect was observed at 30 M lead, higher concentrations had an inhibitory effect.In vivo exposure to lead increased the activity of calmodulin by 45%. Lead had an inhibitory effect on Ca²⁺ ATPase activity in both calmodulin-rich and calmodulin-depleted synaptic plasma membranes, the IC₅₀ values for inhibition being 13.34 and 16.69 M respectively. Exogenous addition of calmodulin (5 g) and glutathione (1 mM) to calmodulin rich synaptic plasma membranes reversed the inhibition by IC₅₀ concentration of lead.In vivo exposure of lead also significantly reduced the Ca²⁺ ATPase activity, resulting in an increase in intrasynaptosomal calcium. Concomitant with the increase in intrasynaptosomal calcium, lipid peroxidation values also increased significantly in lead-treated animals. In addition lead also had an inhibitory effect on depolarization induced Ca²⁺ uptake and the inhibition was found to be a competitive one. The results sugest that lead exerts its toxic effects by modifications of the intracellular calcium messenger system which would have serious consequences on neuronal functioning.     

Safety and efficacy of oral DMSA therapy for children with autism spectrum disorders: Part A - Medical results

Background

This study investigated the effect of oral dimercapto succinic acid (DMSA) therapy for children with autism spectrum disorders ages 3-8 years.

Methods

Phase 1 involved 65 children who received one round of DMSA (3 days). Participants who had high urinary excretion of toxic metals were selected to continue on to phase 2. In phase 2, 49 participants were randomly assigned in a double-blind design to receive an additional 6 rounds of either DMSA or placebo.

Results

DMSA greatly increased the excretion of lead, substantially increased excretion of tin and bismuth, and somewhat increased the excretion of thallium, mercury, antimony, and tungsten. There was some increase in urinary excretion of essential minerals, especially potassium and chromium. The Phase 1 single round of DMSA led to a dramatic normalization of RBC glutathione in almost all cases, and greatly improved abnormal platelet counts, suggesting a significant decrease in inflammation.

Conclusion

Overall, DMSA therapy seems to be reasonably safe, effective in removing several toxic metals (especially lead), dramatically effective in normalizing RBC glutathione, and effective in normalizing platelet counts. Only 1 round (3 days) was sufficient to improve glutathione and platelets. Additional rounds increased excretion of toxic metals.     

Spring Time and Autumn Time Toxic Effects of Copper (II), 3-(2-Furyl) Prop-2-Enal Semicarbazone and [CuCl2(FASC)2] Complex in Mice

In vitro, 3-(2-furyl) prop-2-enal semicarbazone-copper (II) complex [CuCl₂(FASC)₂] presents antimitotic effects. In this work we studied the in vivo seasonal toxic effects in male Swiss mice of CuCl₂, and FASC and the [CuCl₂(FASC)₂] complex. In spring, one injection of CuCl₂8.10^-2 mmol killed 16% of animals after 24 h. Cupric chloride lethal dose was up to 64.10^-2 mmol with 100% mice dead after 24 h. FASC was well tolerated from 0.65 to 1.3 mmol. The complex was 100% lethal with 48.10^?2 mmol. In autumn, mice were more sensitive to CuCl₂ and to the complex with lethal doses up to 32.10^-2 mmol and 8.10^-2 mmol, respectively. On the other hand, FASC was well tolerated. It is concluded that the in vivo toxic effects of CuCl₂ and [CuCl₂(FASC)₂] complex are quite different in spring and autumn.     

Intradermal administration of lipopolysaccharide in treatment of human cancer

 Lipopolysaccharide (LPS) has been recognized as a potent antitumor agent in animal tumor models; however, its use in human cancer therapy has been limited to only one trial, in which LPS from Salmonella was given intravenously. It was not very successful because of poor tumor response and was also toxic. We originally developed LPS prepared from Pantoea agglomerans (LPSp), and this was a well-purified, small-molecular-mass (5 kDa) agent. We chose intradermal rather than intravenous administration in the hope that the former would release LPS slowly into the bloodstream, and thus be less toxic while preserving antitumor activity. In our animal tumor models, intradermal administration was indeed less toxic and more beneficial for tumor regression than intravenous administration. We made a pilot study with intradermal administration of LPSp on the treatment of ten advanced cancer patients. Five of them had evaluable tumor, which had failed earlier to respond to conventional chemotherapy. Cyclophosphamide was also administered in this trial, in anticipation of its synergistic effect with LPSp. In this study LPSp was injected intradermally into each patient twice a week, starting with an initial dose of 0.4 ng/kg, and raising it to 600 or 1800 ng/kg. A 400-mg/m² dose of cyclophosphamide was given intravenously every 2 weeks. After completion of the dose escalation, the treatment was continued for at least 4 months, and it was found that 1800 ng/kg LPSp was well tolerated. A significant level of cytokines was observed in the sera for at least 8 h. These results indicate higher tolerable doses and remarkably more continuous induction of the cytokines than were reported in a previous study by others using intravenous administration. Three of the five evaluable tumors showed a significant response to our combined therapy. Intradermally administered, LPS was less toxic and elicited a tumor response in combination with cyclophosphamide; it can thus can be applied to cancer treatment even in humans. Received: 3 August 1995 / Accepted: 2 April 1996     

The actions of leptin on survival and hydrogen peroxide toxicity in primary mixed glial cells of rat

Studies indicate that leptin is involved in not only energy expenditure and food intake, but also in protection against apoptosis, in inflammation and in stimulation of proliferation in many cell types. However, leptin treatment increases the oxidative stress in many cell culture studies. This contradiction evoked a question of whether leptin acts as an oxidant or antioxidant on glial cells. We investigated the effect of leptin on glial cell survival and hydrogen peroxide (H₂O₂)-induced toxicity in vitro. The survival rate of the cells was determined by using 3-(4,5-D-methylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, thyazolyl blue (MTT) method. The cells obtained from the whole brain of 1–3 day-old rat were treated with 1, 10, 100 and 1000 ng/mL leptin for 24 or 72 h. Either the pretreatment of leptin alone for 5 h or leptin combined simultaneously with H₂O₂ or well known antioxidant glutathione (GSH) were applied to the cells. Malondialdehyde (MDA) levels were measured in cell lysates to which leptin was added for 24 h. The 100 and 1000 ng/mL leptin treatment for 72 h increased the glial viability by 19% and 36%, respectively. The dose of H₂O₂ that killed 75% of the cells was determined as 100 μM. GSH at different doses was applied as a positive control to the cells and the dose of 500 μM completely eliminated toxic effect of 100 μM H₂O₂. Either the pretreatment of leptin alone for 5 h or leptin combined simultaneously with H₂O₂ could not eliminate H₂O₂-caused toxicity. Furthermore, respective leptin doses did not change the glia MDA level. We suggest that leptin can increase glia survival dose dependently, but can not eliminate H₂O₂-induced oxidation in primary mixed glial cell culture.     

The toxicity of aphicide residues to beneficial invertebrates in cereal crops

The toxicity of dimethoate, deltamethrin and pirimicarb residues to Bembidion lampros and Coccinella septempunctata was evaluated by confining groups of insects to winter wheat foliage and soil for 24 h at different times after treatment in the field. Flag leaf residues were found to be more toxic than first leaf residues: soil residues were the least toxic with pirimicarb showing virtually no soil toxicity. In general, dimethoate and deltamethrin showed similar levels of foliar toxicity with flag leaf toxicity on the first day after treatment being in the range 60–80% for B. lampros; deltamethrin was however, less toxic than dimethoate at ground level. Both of these products were more toxic than pirimicarb. The long-term exposure of insects, surviving the 24 h bioassays, to treated soil at different times following application resulted in further mortality and provided estimates of the maximum levels of mortality that populations of predators might suffer migrating into the crop at different times following application. Dimethoate was shown to be particularly harmful at the current recommended field application rate and reduced doses were proposed to limit the severity of the initial effects.